re: progress tle , high drag factors

From: Walter Nissen (
Date: Thu Aug 23 2001 - 15:38:00 PDT

  • Next message: Tom Troszak: "Re: FW: Shuttle water dump while attached to ISS" ("Sebastian Stabroth") writes:
    > > If a drag factor is too high, the object will arrive late.
    > Hmm, it should exactly be the opposite in orbital motions. If an object
    > loses height
    > because of high drag, it travels faster and arrives sooner at your point of
    > observation.
    Thanks for your comment.
    We are saying the same thing.
    Let me restate what I said.
    If a drag factor in an elset is higher than the true drag experienced by
    the object traveling through the upper atmosphere, then if the observer
    looks for the object based on an ephemeris generated by a propagator
    using the elset, then the observer will see the object later than
    expected.             (Observers recognize this as a common experience).
    The higher the drag, the EARLIER the object will appear.
    I capitalize EARLY and its inflected forms to warn the observer of a
    potential conflict with the old aphorism:
      If you are a minute early, you will see it.
      If you are a minute late, you won't.
    For this reason, when I generate indications of visibility, I lean
    toward elsets with high drag factors.
    Someone else will have to write the 8 or 10 paragraphs needed to explain
    the ambiguities, abstractions, idioms, vagaries of the English language,
    and other subtleties which bring us here.
    Walter Nissen
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